1. Field of the Invention
The present invention relates to a light-emitting device which emits light from a light-emitting element such as a light-emitting diode (referred to as LED hereinafter) and in particular, to a light-emitting device with a high efficiency of light extraction.
2. The Related Art of the Invention
There is well known an earlier LED chip with an improved efficiency of light extraction, for instance, a LED chip with a convex and a concave portion formed on a light extraction side in a substrate (refer to Japanese Unexamined Patent Publication No. 2002-319708 (Paragraphs [0022]-[0024], FIG. 2)).
FIG. 1 shows the earlier LED chip. The LED chip 100 forms on a sapphire substrate 101 a nitride semiconductor layer made of a GaN buffer layer 102, an n-type semiconductor layer 103, and a p-type semiconductor layer 104. Further, a p-side electrode 105 is disposed on the p-type semiconductor layer 104 and an n-side electrode 106 is disposed on the n-type semiconductor layer 103. The LED chip 100 is flip chip bonded on a mounting substrate 110 by bumps 130a and 130b. And a surface of the sapphire substrate 101 opposite to a surface where the nitride semiconductor layer is formed is grinded by an abrasive with a regulated size of particles, to form irregular surfaces 110a and 101b having a depth of approximately 1 μm. Since light emitted at a light-emitting portion of the nitride semiconductor layer is reflected in random directions by these irregular surfaces, repetition of total reflection of light inside the LED chip 100 is restricted to improve light extraction efficiency.